Apparatus for starting and controlling electric discharge devices



Se t 3, 195/ .1. c. MOERKENS 2,805,364

APPARATUS FOR STARTING AND CONTROLLING ELECTRIC DISCHARGE DEVICES FiledAug. 14, 1951 INVENTOR Jozef Cornelis Moerkens By WW Agen APPARATUS FORSTARTING AND CONTROLLING ELECTRIC DISCHARGE DEVICES Jozef CornelisMoerkens, Eindhoven, Netherlands, as-

signor, by mesnc assignments, to North American Philips Company, Inc.,New York, N. Y., a corporation of Delaware Application August 14, 1951,Serial No. 241,782

Claims priority, application Netherlands September 22, 1950 4 Claims.(Cl. 315--95) The present invention relates to a circuit arrangement forstarting electric discharge tubes. More particularly, the inventionrelates to devices comprising a discharge tube which is connected inseries with a capacitative im-v pedance and comprises at least onethermionic electrode, whose end remote from the connecting terminals ofthe device is connected to the other electrode of the tube prior to itsignition.

During operation such a tube takes a current leading the supply voltage.This permits an excellent power factor to be obtained if the device alsocomprises an inductively stabilized tube taking a lagging current.Furthermore, the stroboscopic effect of a single tube is greatly reducedwith the use of leading and lagging tubes, because the dark periods ofthese tubes do not simultaneously occur.

nited States Patent '0 The warming up of the thermionic electrode. of aIn order to heat the thermionic electrode of the capacii tativelystabilized tube rapidly to its emitting temperature, an auxiliaryinductor, also termed compensator, is.usually inserted in the parallelcircuit of the tube, i. e. in the electrode connection adapted to beinterrupted and intended for ignition of the tube. The compensator is soproportioned that the preheating circuit of the thermionic electrode istraversed by a current exceeding 1.2 times and preferably 1.3 to 1.8times the prescribed discharge current of the tube. On ignition thecircuit of the compensator is interrupted, so that this element is outof action during normal operation of the tube.

The present invention provides other means for preheating thermionicelectrodes with acurrentrnaterially exceeding the operating current.

According to the invention, the" papacitative seriesimpedance is soproportioned that, when connected directly to the supply, it consumes acurrent exceeding 1.2 times and preferably 1.3 to 1.8 times theoperating current of the tube, at leastpart of the capacitativeseriesirnpedance having connected in parallel with it an inductivebranch which is interrupted during the preheating period of thethermionic electrode but closed during operation of the tube, and whichis so proportioned that the tube is traversed only by approximately 1.0times the operating current during normal operation.

In a particularly advantageous embodiment of the invention, theinductive parallel branch consists of an inductance in series with asecond discharge tube also comprising at least one thermionic electrode,whose end remote from the connecting terminals of the device is adaptedto be connected through a switch to the second electrode of this secondtube, this switch being open during the passage of preheating currentthrough the thermionic electrode of the first tube. The switch of theinductively stabilized tube may be a switch which is 2,805,364 PatentedSept. 3, 1957 2 open in the deenergized condition and the closing periodof which corresponds to at least the preheating period of the thermionicelectrode of the capacitatively stabilized tube.

In order that the invention may be readily carried into efiect, it willnow be described in detail with reference to the accompanying drawing,in which the single figure is a preferred embodiment of the circuitarrangement of the present invention. The reference numeral 1 denotes adischarge tube, for example a fluorescent lowpressure mercury-vapourdischarge tube. Through a capacitor 2 and an inductor 3 the tube isconnected to terminals 4 and 5 intended to be connected to a source ofalternating current, for example a power supply of approximately 220volts at 50 cycles per second suitable for feeding the tube. Thecapacitance l/wC of the capacitor 2 exceeds the inductance @L of theinductor 3, so that at a frequency of 50 cycles per second theseriesconnection of these two elements constitutes a capacitativeseries-impedance of the tube. The tube comprises thermionic electrodes 6and 7, Whose ends remote from the connecting terminals may be connectedby means of a switch, for example a glow discharge switch that may bebridged by a small capacitor of approximately 10,000 microfarads. As isknown, the glow discharge switch is a bimetallic switch located in agaseous atmosphere said switch being open in the cold state and being soproportioned that its electrodes, when connected to the supply voltage,engage each other but do not contact upon connection to the tubevoltage. V

In addition, the device comprises a discharge'tube 9 which is connected,through an inductor 10, in parallel with the inductor 3 and thecapacitor 2. The point 11 between terminal 4 and inductor 3 mayalternatively be located at a tapping point of they inductor .3 orbetween said inductor and the capacitor 2. The tube 9 comprises twothermionic electrodes 12, 13 whose ends remote from the connectingterminals 4 and 5 are adapted to be connected through a switch 14, whichmay also be a glow discharge switch bridged by a small capacitor.

The tubes 1 and 9 are, for example,'fluorescent tubes approximately 120cms. long and about 318 mms in diameter, which during normal operationconsume '40 watts energy with an operating voltage of approximatelyvolts and a current of approximately 440 milliamperes and 420milliamperes, respectively. The preheating of the thermionic electrodesto the emitting temperature requires a current materially exceeding theaforesaid prescribed operating current of approximately 440 milliamperesand 420 milliamperes, respectively. In order to Warm up the thermionicelectrodes. 6 and 7 of tube 1, the elements 2 and 3am soiproportionedthat a current of approximately 580 milliamperes .passes through saidelectrodes with closed switch and open switch 14.

The warming up of the thermionic electrodes 12 and 13 of tube 9 does notinvolve any appreciable diificulty. As is customary, the inductor 10 isso proportioned relatively to the magnetic saturation as ,to produce thedesired pre-heating current through the thermionic electrodes 12 and 13with closed switch 14 during normal operation of the tube 1.

When using glow discharge switches 8 and 14, which are open in the coldstate and supplied from a source of current of approximately 220 voltsat 50 cycles per second, the device operates as follows.

On connecting terminals 4 and 5 to the power supply, substantially thefull supply voltage is operative across switch 8, thus producing a glowdischarge therein, which causes said switch to close. Subsequently thethermionic electrodes 6 and 7 of tube 1 are warmed up eitherintermittently or continuously in accordance with the cons'truction ofsaid swi'tch. As soon as the emitting temperatu're of the thermionicelectrode is reached the tube 1 strikes on opening switch 8. In theclosed state of switch 8, a glow discharge tending to close switch 14also occurs. On reaching the closed state, the thermionic electrodes 12and 13 of tube 9 are warmed up so that said tube is also adapted tostrike. It is advisable that the closing period of switch 14 should besuch as to correspond to at least the preheating period of thethermionic electrodes 6 and 7 of tube 1, since otherwise the ignition ofthe tubes is delayed.

From the foregoing it will be seen that the device does 'not compriseany reactive element which is not utilized during operation of thetubes.

Parallel connection of the inductive tube branch to part of thecapacitative tube branch yields particular advantages which areevidentfrom the following:

During normal operation of the tubes a voltage of approximately 100volts with a current of approximately 420 milliamperes is operativeacross the inductor 10, so that the power of this inductor isapproximately 42 volt amperes; With a current of approximately 450millia'mperes a voltage of approximately 100 volts is operative acrossthe inductor 3 and a voltage of about 260 volts across the cpaacitor '2,likewise during normal operation. Consequently, the power of inductor 3is about 45 volt amperes and that of the capacitor 2 about 120 voltamperes. With the same 40 watt tubes, when connected to 220 volts intube branches independent of each other and lagging and leadingrespectively, the inductor of the lagging branch requires a power ofabout 70 volt amperes. The inductor of the leading branch requires apower of about 60 volt amperes and the capacitor of the last-mentionedbranch a power of about 160 volt ampres. Consequently, in the deviceaccording to the invention, all the reactances for stabilizing the tubesare smaller and cheaper than in tubes supplied independently of oneanother.

While the invention has been described by means of a specific exampleand in a specific embodiment, I do not wish to be limited thereto, forobvious modifications will occur to those skilledin the art withoutdeparting from the'spirit and scope of the invention.

What I claim is:

1. A circuit arrangement for starting electric discharge tubes,comprising a source of alternating current at a given frequency, agas-filled electric discharge tube having a pair of electrodes at leastone of which is thermionic and adapted to operate with a given current,a capacitative impedance connected in series with said source and 2. Acircuit arrangement for starting electric discharge tubes, comprising asource of alternating current at a given frequency, a gas-filledelectric discharge tube having a pair'of electrodes at least one ofwhich is thermionic and adapted to operate with a given current, acapacitative impedance connected in series with said source and saidtube, normally-open switching means interconnecting the electrodes ofsaid tube in series with said capacitative impedance and said source,said capacitative impedance having an impedance at which a currentexceeding 1.2 times said given current traverses the thermionicelectrode when said switching means is closed, a predominantly inductivecircuit connected in parallel with a portion of said capacitativeimpedance, said inductive circuit comprising an inductor, a secondgas-filled discharge tube having a pair of electrodes at least one ofwhich is thermionic connected in a series with said inductor, anormallyopen switch interconnecting the electrodes of said second tubeand adapted to be closed a pre-determined time interval after theswitching means is closed, said inductive circuit having an impedance atwhich a current of about 1.0 times said given current traverses saidfirst tube when ignited, and means for closing said switching means tothereby effect ignition of said tube.

3. A circuit arrangement for starting electric discharge tubes,comprising a source of alternating current at a given frequency, agas-filled electric discharge tube having a-pair of electrodesat leastone of which is thermionic and adapted to operate with a given current,a capacitative impedance connected in series with said source and saidtube, normally-open glow discharge switching means said tube,normally-open switching means interconnecting the electrodes of saidtube in series with said capacitative impedance and said source, saidcapacitative impedance having an impedance at which a current exceeding1.2 times said given current traverses the thermionic electrode whensaid switching means is closed, a predominantly inductive circuitconnected in parallel with a portion of 'said capacitative impedanceincluding a normally-open interconnecting the electrodes of said tube inseries with said capacitative impedance and said source, saidcapacitative' impedance having an impedance at which a current exceeding1.3 times said given current traverses the thermionic electrode whensaid switching means is closed, a predominantly inductive circuitconnected in parallel with a portion of said capacitative impedance,said inductive circuit comprising an inductor, a second gas-filleddischarge tube having a pair of electrodes at least one of which isthermionic connected in series with said inductor, a normally-open glowdischarge switch interconnecting the electrodes of said second tube andadapted to be closed, a predetermined time interval after the switchingmeans is closed, said inductive circuit having an impedance at which acurrent of about 1.0 times said given current traverses said first tubewhen ignited, whereby application of potential will close said switchingmeans and thereby etfect ignition of said tube.

4. A circuitarrangement as :claimed in claim 3 in which thepre-deterrnined time interval after which the switch closes correspondsto the time for preheating the thermionic electrode of the first tube.

References Cited in'thefile of this patent UNITED STATES PATENTS2,056,661 .Foulk'e' Oct. 6, 1936 2,298,935 Freeman Oct. 13, 19422,358,810 Karash Sept. 26, 1944 2,363,868 Karash Nov. 28, 1944 2,386,914Slepian Oct. 16, 1945 2,423,031 Kurtz June 24, 1947

